Decompression device for internal combustion engine



O United States Patent 1 13,54s,799

[72] Inventor .losefJohann Lang, 3,057,336 10/1962 Hatz, Jr. 123/182 18Blrkenstrasse, 8018 G ra1lng, Germany 3,146,772 9/1964 123/ 182 [21]Appl. No. 801,965 3,319,619 5/1967 123/182 [22] Filed Feb. 25, 19693,342,169 9/1967 Farney et a1. 123/182 Pale-med 9 9 0 FOREIGN PATENTS IPmmy Feb-29,1968 882,033 11/1961 Great Britain 123/182 [33] Germany 31]No. 1,601,973 Prlmary ExammerWendell E. liums Attorney- Larson, Taylorand Hinds [54] DECOMPRESSION DEVICE FOR INTERNAL COMBUSTION ENGINE 5Claims 4 Drawing Figs ABSTRACT: A decompression device for temporarilyholding 1 33/182 open the exhaust valve of an internal combustionengine. In a hit-CI 13/03 first position, a shaft permits normaloperation of the valve ofSearch and in a second position the shaftprevents full closing of the valve. An automatic device moves the shaftfrom the second [56] References and position to the first position atthe desired time to automati- UNITED STATES PATENTS cally terminatedecompression by permitting the valve to 1,900,367 3/1933 Schargorodsky123/182 close.

DECOMPRESSION DEVICE FOR INTERNAL COMBUSTION ENGINE BACKGROUND Thisinvention relates to internal combustion engines, and in particular itrelates to a new and improved decompression device for an internalcombustion engine.

SUMMARY OF THE INVENTION This invention relates to a decompressiondevice for combustion engines, for example, injection combustionengines, having an exhaust valve controlled through a plunger rod, thisdevice comprising a decompression cam, which may be a decompressionshaft having a milled out flattened portion, which acts on a controlpart of the plunger rod and is adapted to be moved to a decompressioncutout position by an automatic means which includes a driving'platewhich is coupled to the decompression shaft and a driver cooperatingwith this plate and operable so that, when the plunger rod moves in onesense this driver engages the driving plate and, when the plunger rodmoves in the other sense, the driver is disengaged from the plate underthe action of spring means.

It is an object of the present invention to devise a decompressiondevice of this type which is compact, which operates reliably and ismade from a minimum of parts. Moreover, it is intended that theconstructional element will be arranged in such a way that they are notkept in movement during the running of the engine and consequently donot add to the inertia of the moving operating parts.

To meet these objects, the present invention provides an arrangement inwhich the driver is in the form of a driving plunger which is movable atleast approximately parallel to the said plunger rod and is actuated byone of the operating parts, for example, from the plunger rod itself,said driving plunger being mounted in resiliently yielding fashion in anabutment body, separate from the operating parts of the device, whichbody is adjustable by the decompression cam and acts as a stop for theoperating part which actuates the driving plunger, for example the saidplunger rod.

In a preferred form of the invention and in accordance with anotherfeature of the latter the abutment body has a cylindrical part mountedin a housing of the decompression device and has an arm which engagesaround the plunger rod and a flange with a substantially sphericalopening for the driving plunger.

It is further advantageous in this connection to use a further featureof the invention which resides in the fact that a cylindrical abutmentmember is adjustably secured to the plunger rod, and this membercooperates on the one hand with the driving plunger and, on the otherhand with an abutment surface of the abutment body.

Thus, it is an object of this invention to provide a new and.

improved decompression device for an internal combustion engine.

It is another object of this invention to provide a new and improveddecompression device made from a minimum of parts and wherein the partsare not movable under normal engine operation, so that they do not addto the inertia of the moving parts.

Other objects and the attendant advantages of the invention will becomeapparent from the detailed description to follow.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention isillustrated in the accompanying drawings in which:

FIG. 1 is a cross section through the decompression device, and showingalso the exhaust valve;

FIG. 2 illustrates a detail of the mechanism seen in FIG. 1 but turnedapproximately 90 in the counterclockwise direction relative to theposition of FIG. 1; and

FIG. 3 and 4 show the assembly in different operating positions. I

Arranged in the housing 10 of an injection combustion engine of knownconstruction, a part of which is shown at 1. is an exhaust valve 2 whichis pressed against its valve seat 3 by a closure spring 4 which actsbetween a fixed part of the combustion engine 1 and a collar 5 fixed onthe valve stem 6, the latter being operationally integral with a plunger16. In prac tice the plunger rod 16, which is raised and lowered by acaM l4 and a sliding connecting piece 12, engages a rocker lever, shownsymbolically at 7, which moves the exhaust valve member 2 downwardly (asshown in FIG. 1) to separate the valve member 2 from the valve seat 3and thereby move the valve in the opening direction. When plunger rod 16moves up the valve opens, while thelatter is closed by spring 4 actingon collar 5 when the rod moves down.

To assist the hand turning of the engine during starting, the exhaustvalve is prevented from fully closing with the help of the decompressiondevice whereby compression is not developed in the operating chamber ofthe engine such as would render the turning difficult. The decompressiondevice comprises a decompression shaft 18 which is mounted at which isfixed relative to housing 10 so as to extend transversely in relation tothe plunger rod 16, and a setting lever (not shown) is fastened to theend of this spindle where it projects from housing 10. Shaft 18 isflattened at 18a by the provision of a milled out portion. Seateddirectly on this flattened portion in housing l0b which is also fixedrelative to housing 10 is an abutment body 22 which represents thedecompression stop and is loaded by a spring 28 and is movable. If thedecompression spindle is set so that the milled portion is locatedbeneath the abutment body 22 (FIG. 1) the plunger rod 16 is able to movewithout obstruction to permit closing of the exhaust valve 2. Ifhowever, the shaft 18 is turned so that the cylindrical part of thesurface thereof is opposite body 22 (FIGS. 2, 3 and 4), the cylindricalstop screw 30 strikes the abutment surface 220 during the downwardmovement of the plunger rod 16 and prevents the exhaust valve 2 fromfully closing.

Abutment body 22 has an opening 22d through which the plunger rod 16passes, and it also has'a flange 22a with a spherical opening 22b inwhich is guided a driving plunger 24. A spring 26 seated between part22a and the end 24b of the driving plunger 24 holds it in engagementwith part 220. The lower end 240 of the driving plunger 24 is in theform of a striker tooth which cooperates with teeth 20:; on theperiphery of a driving plate 20. This latter is fastened to shaft 18.

The abutment screw 30 on the threaded portion 16a of the plunger rod 16can be retained in its setting by means of a lock nut 32.

The decompression device described operates as follows:

When the engine is running or is stopped the decompression device is inthe inoperative position seen in FIG. 1. In this position the drivingplunger 24 cannot be reached by part 30 on the plunger rod 16 so that,as has already been briefly stated, the exhaust valve 2 closes fullyunder the influence of spring 4 and the plunger rod 16 moves idly inrelation to the stationary parts 18,20, 22 and 24.

If, however, a stationary engine is to be started through the agency ofthe decompression device and the latter is to be automatically cut outafter starting, the shaft 18 is to be moved by means of its settinglever from the rest position seen in FIG. 1 of the drawings into theoperative position shown in FIGS. 2 and 3. As a result of this abutmentbody 22 is adjusted upwards by the full cylindrical periphery of shaft18 so that the head 24b of the driving plunger 24 and the stop surface22 c of the abutment body 22 are brought into the path of travel of theabutment screw 30 on the plunger rod 16. When the engine is turned, andat each downward stroke of the parts 16, 30, on the one hand the drivingplate 20 and shaft 18 are turned through one tooth by the striker tooth240 of the driving plunger 24, and on the other hand the plunger rod 16at its lowest point is held lifted by the amount S (FIG. 4) so that thevalve 2 cannot close fully and hence no compression can develop in theoperating chamber of the engine. During the upward movement of theplunger rod 16, however, the striker tooth 24c slides over the nexttooth of the driving plate 20 and drops ultimately behind that nexttooth of the set of teeth 20a; and the striker tooth then turns theplate 20 one tooth during the next downward movement of the plunger 16.This progression of events is repeated until the striker tooth 24creaches the untoothed zone 20b of the driving plate 20 at which positionthe milled portion 18a of shaft 18 permits the return of abutment body22 to the rest position of FIG. 1. The decompression is terminated.

The period over which this decompression is effective can be adjusted byturning shaft 18 and appropriately adjusting teeth 200 of the drivingplunger 24. It will be apparent that the decompression device accordingto the invention comprises only a few constructional parts which do notmove during the actual running of the machine and moreover are groupedin a compact arrangement associated with the valve-operating parts.Consequently the decompression device according to i this invention canbe installed in all combustion engines without any difficulty and alsobuilt into finished engines.

Although the invention has been described in considerable detail withrespect to a preferred embodiment thereof, it will be apparent that theinvention is capable of numerous modifications and variations apparentto one skilled in the art without departing from the spirit and scope ofthe invention.

lclaim:

l. A decompression device for selectively preventing full closing of anexhaust valve of an internal combustion engine comprising, incombination: a plunger rod for opening and closing the valve, adecompression cam and an abutment body, the decompression cam having afirst position whereat it permits normal opening and closing of thevalve and a second position whereat it moves the abutment body into thepath of an operating member movable with the plunger rod. to preventfull closing of the valve; a decompression cutoff means forautomatically turning the decompression cam from said second position tosaid first position, said cutoff means comprising a plate turnable withthe decompression cam and a driving plunger mounted in a resilientlyyielding manner in said abutment body and movable in a directiongenerally parallel to the plunger rod, said driving plunger positionedto be engaged by the said operating member, when the decompression camis in its second position, to act on the plate to turn the decompressioncam towards its first position, before the movement of the operatingmember is limited by the abut ment body.

2. A decompression device according to claim 1 wherein the abutment bodyhas a cylindrical part slidably mounted in a housing of thedecompression device, and an arm which slidably engages around theplunger rod, and a flange part with a substantially spherical openingfor the driving plunger.

3. A decompression device according to claim 2 wherein a cylindricalabutment member is adjustably secured to the plunger rod, and whereinsaid abutment member cooperates both with the driving plunger for urgingthe same against the said plate, and also with an abutment surface ofthe abutment body for limiting movement of the abutment member and henceof the plunger rod.

4. A decompression device according to claim 3 wherein saiddecompression cam is a shaft having the plate fixed thereon and having aflattened portion for cooperating with the cylindrical part of theabutment.

5. A decompression device, according to claim 4, wherein said plate hasa plurality of teeth thereon and wherein said driving plunger acts onthe plate to turn the same by one tooth during each cycle of movement ofthe plunger rod, until the plate, and hence the decompression shaft hasreached the said first position.

